%算alpha
function alpha = compute_alpha(a_coef, normal, b_edge_value)
alpha = 0;
for i = 1 : 3
    edge_value = a_coef*b_edge_value(:,:,i);
    normal_value = sum(normal(i,:));
    alpha_value = zeros(1,4);
    for j = 1 : 4
        alpha_value(j) = abs(edge_value(j)*normal_value);
    end
    tmp_alpha = max(alpha_value);
    alpha = max([alpha,tmp_alpha]);
end
end